Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

Contents lists available at ScienceDirect

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa

Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory Noureddine Issaoui a, Houcine Ghalla a, S. Muthu b,⇑, H.T. Flakus c, Brahim Oujia a,d a

Quantum Physics Laboratory, Faculty of Sciences, University of Monastir, Monastir 5079, Tunisia Department of Physics, Sri Venkateswara College of Engineering, Sriperumbudur 602105, India Institute of Chemistry, University of Silesia, 9 Szkolna Street, 40-006 Katowice, Poland d Faculty of Science, King Abdulaziz University, Saudi Arabia b c

h i g h l i g h t s

g r a p h i c a l a b s t r a c t

 The FT-IR, FT-Raman, spectral

The Fourier transform infrared and Raman spectra of 3-thiophenecarboxylic acid are recorded in solid phase, the harmonic vibrational frequencies, infrared intensities, Raman activities, bond length, bond angle are calculated by DFT methods using 6-311++G(d,p) basis set. To predict reactive sites for electrophilic and nucleophilic attack for the title molecule, molecular electrostatic potential (MEP) at the B3LYP/ 6-311++G(d,p) optimized geometry is calculated.

investigation of title molecule has been performed using DFT methods.  Optimized parameters were calculated.  The complete assignments are performed on the basis of the potential energy distribution (PED).  The redistribution of electron density has been discussed.  Hyperpolarizability, HOMO and LUMO energies were calculated.

a r t i c l e

i n f o

Article history: Received 24 May 2014 Received in revised form 28 July 2014 Accepted 8 October 2014 Available online xxxx Keywords: DFT FTIR 3-Thiophenecarboxylic acid HOMO–LUMO

a b s t r a c t In this work, the molecular structure, harmonic vibrational frequencies, UV, NBO and AIM of 3-thiophenecarboxilic acid (abbreviated as 3-TCA) monomer and dimer has been investigated. The FT-IR and FTRaman spectra were recorded. The ground-state molecular geometry and vibrational frequencies have been calculated by using the Hartree–Fock (HF) and density functional theory (DFT)/B3LYP methods and 6-311++G(d,p) as a basis set. The fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with VEDA program. Comparison of the observed fundamental vibrational frequencies of 3-TCA with calculated results by HF and DFT methods indicates that B3LYP is better to HF method for molecular vibrational problems. The difference between the observed and scaled wavenumber values is very small. The theoretically predicted FT-IR and FTRaman spectra of the title compound have been constructed. A study on the Mulliken atomic charges, the electronic properties were performed by time-dependent DFT (TD-DFT) approach, frontier molecular orbitals (HOMO–LUMO), molecular electrostatic potential (MEP) and thermodynamic properties have

⇑ Corresponding author. Tel.: +91 9443690138. E-mail addresses: [email protected], [email protected] (S. Muthu). http://dx.doi.org/10.1016/j.saa.2014.10.008 1386-1425/Ó 2014 Elsevier B.V. All rights reserved.

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

2

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

been performed. The electric dipole moment (l) and the first hyperpolarizability (b) values of the investigated molecule have been also computed. Ó 2014 Elsevier B.V. All rights reserved.

Introduction The heterocyclic compounds are extensively distributed in nature and are essential to life in various ways [1]. The chemistry of heterocyclic compounds is one of the most complex branches of organic chemistry. It is evenly interesting for its theoretical implications, for the diversity of its synthetic procedures, and for the physiological and industrial significance of heterocyclic compounds. The studies of heterocyclic compounds have been an interesting field for a long time in medicinal chemistry. A number of heterocyclic derivatives containing sulphur or (and) nitrogen atom serve as a unique and versatile scaffolds for experimental drug design [2]. Thiophene and a number of its derivatives [3–6] are significant in fine chemical industries as intermediates to many products for pharmaceutical, agrochemical, dyestuffs, and electronic applications. In general, it can be considered that the carboxylic group in thiophenecarboxylic acids is much the same as in any organic compound. It undergoes esterification to give yields almost identical with those with benzoic acid. The ability of carboxylic acids to behave as hydrogen bond donor–acceptors is responsible for many interesting chemical [7] and biochemical [8] properties of these compounds. The study of the interaction between furan as a proton acceptor and a proton donor is important to understand the properties of Thiophene and the related hydrogen bond. In this context, the study of the structural properties of Thiophene derivatives is important in relation to the pharmacological activities and to the identification of these compounds by means of vibrational spectroscopy. Thus, as a continuation of structural and vibrational studies related with heterocyclic compounds of great interest, in this work we considered the 3-thiophenecarboxylic acid (3-TCA). 3-TCA is one of the most important heterocyclic compound having varied biological activities with great scientific interest. In 1964, Hudson and Robertson have studied the crystal structure of the title molecule [9]. They showed that the 3-TCA is essentially planar. Crystals of 3-TCA are also monoclinic, the space group is C2/c and Z = 8. The unit cell parameters are a = 13.601 Å, b = 5.447 Å, c = 15.054 Å and b = 99.1°. The molecules of 3-TCA in the lattice are linked together by the OAH  O hydrogen bonds, forming cyclic approximately centrosymmetric dimers [9–11]. In this case the hydrogen bond dimer should be responsible for the main spectral properties of the crystal in the mOAH band frequency range. Recently (in 2011), 3-thiophene carboxylic acid molecule has been investigated by Chandra et al. [12]. The optimized structural parameters and computed vibrational wavenumbers of the neutral and the anionic forms of the 3-TCA molecule are provided from the theoretical calculations using density functional theory (DFT) but, the effect of hydrogen bonding, charge transfer, NLO and thermodynamic properties has not been discussed. For this reason and for their biological and industrial significance, we have proposed the vibrational assignments of 3-TCA according to the characteristic group frequencies observed in FT-IR and FT-Raman spectra. Besides, we interpreted the calculated spectra in terms of potential energy distributions (PEDs) and also made the vibrational assignments based on these PED results. Furthermore, the structure– chemical reactivity relations and the nonlinear optical properties of the title compound have been undertaken for the first time. Recall that, the nonlinear optics is one of a few research frontiers where tremendous interest arises not only from the request for

understanding of new physical phenomena but also from the potential technological applications [13,14].

Experimental details The 3-thiophenecarboxylic acid was purchased from Sigma– Aldrich Chemical Company (USA). FT-IR spectrum of title compound was recorded in the region 4000–400 cm1 on JASCO6300 spectrometer with samples in the KBr. The FT-Raman spectrum of the molecule was obtained in the region 4000–400 cm1 using Bruker RFS 100/s FT-Raman spectrophotometer with a 1064 nm Nd:Yag laser source of 150 mW power. The spectral resolution is 2 cm. The absorption spectra in which we have been compared our theoretical results were recorded on a Shimadzu 2010 PC UV–Vis spectrophotometer [12].

Quantum chemical calculations The molecular geometry optimization, vibrational spectra and interaction energies calculations were performed with the Gaussian 03 software package [15], by using DFT and ab initio level [16,17] to characterize all stationary points as minima. We have utilized two different methods namely B3LYP and HF for the computation, which have been performing very well both for geometry optimization and many other molecular properties. The triple split valence basis set along with the diffuse and polarization functions: 6-311++G(d,p) basis set were used for calculations on the investigated systems. The optimized molecular structure of 3-TCA monomer and dimer are given in Fig. 1. The relaxed potential energy scan was carried out for 3-TCA monomer using the DFT/B3LYP/6311++G(d,p) level of theory, by varying CCC@O dihedral angle and optimizing the remaining molecular parameters for each fixed dihedral angle. The results are reported in Fig. 2 for the whole torsional profiles. The geometrical structure corresponding to the lowest minima in the potential energy scan has been used as the starting point for the optimization of the structure at the higher level of theory as well as the basis set. The calculated parameters have been compared with the spatial coordinates of 3-TCA as obtained from X-ray structure analysis [9,11] and also from the theoretical study reported by Chandra et al. [12]. Optimized structural parameters were then used for the calculation of vibrational wavenumbers. The positive value of all the calculated wavenumbers confirms the stability of optimized geometry. Due to the neglect of anharmonicity effect at the beginning of calculation, initially the predicted vibrational wavenumbers are found to be disagreement with experimental wave numbers. Further, these discrepancies are overcome by applying the scale factors. In order to improve the calculated values in agreement with the experimental values, it is necessary to scale down the calculated harmonic frequencies. The theoretical harmonic frequencies were scaled by the aid of the Spesca program [18]. The calculated IR and Raman spectra have been shown in Figs. 3 and 4 and are found to match well with the experimental spectra. The assignments of the calculated normal modes have been made on the basis of the corresponding PEDs. The PEDs are computed from quantum chemically calculated vibrational frequencies using VEDA4 program [19]. Gauss View program [20] has been considered to get visual

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

3

Fig. 1. The optimized geometry of 3-thiophenecarboxylic acid molecule and its hydrogen bonded dimer with atoms numbering calculated by B3LYP/6-311++G(d,p) method.

Fig. 2. Potential energy surface scan of 3-thiophenecarboxylic acid with dihedral angle C3AC4AC9AO12.

animation and also for the verification of the normal modes assignment. The correlation graphic which describes harmony between the calculated and experimental wavenumbers is shown in Fig. 5. As can be seen from Fig. 5, the experimental fundamentals have good correlation with B3LYP. The relations between the calculated and experimental wavenumbers are linear and described by the following equation:

tCal ¼ 0:9501texp  961 for the monomer tCal ¼ 0:9718texp  50 for the dimer We calculated R2 values between the calculated and experimental wavenumbers. We found the following values for the correlation parameter (R2): 0.9995 for the monomer and 0.9993 for the dimer. As a result, the performances of the B3LYP method with respect to the prediction of the wavenumbers within the molecule were quite close. The absolute Raman intensities were calculated from the Raman activities (Si), obtained with the Gaussian 03 program,

and using the following relationship derived from the intensity theory of Raman scattering [21,22]:

Ii ¼

f ðm0  mi Þ4 Si mi ½1  expðhcmi =kT

ð1Þ

Here m0 is the laser exciting wavenumber in cm1. In this work, we have used the excitation wavenumber m0 = 9398.5 cm1, which corresponds to the wavelength of 1064 nm of a Nd:YAG laser), mi is the vibrational wavenumber of the ith normal mode (cm1), while Si is the Raman scattering activity of the normal mode mi. f is a suitably chosen common normalization factor for all peak intensities (is a constant equal to 1012). h, k, c and T are Planck and Boltzmann constants, speed of light and temperature in Kelvin, respectively. Density functional theory has also been used to calculate the dipole moment, mean polarizability and first static hyperpolarizability based on the finite field approach. The electronic absorption spectrum requires calculation of the allowed excitations, the oscillator strengths and the HOMO–LUMO energies. The theoretical UV–Vis spectrum has been calculated. The calculation was based on TD-DFT method with 6-311++G(d,p) basis set. Recall that, the

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

4

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

Fig. 3. Experimental and theoretical Infrared spectra of 3-thiophenecarboxylic acid.

time dependent DFT (TD-DFT) is proved to be a powerful and effective computational tool for the study of ground and excited state properties. The natural bonding orbital (NBO) calculations [23–25] were performed using Gaussian 03 package [15] also at the same level in order to study the stabilities of 3-TCA monomer and dimer. The NBO calculation used to understand various second order interactions between the filled orbitals of one subsystem and vacant orbitals of another subsystem, which is a measure of the intermolecular delocalization or hyper conjugation. The second order perturbation theory analysis of Fock matrix in NBO basis of 3-TCA was carried out to evaluate the donor–acceptor interactions. The interactions result is a loss of occupancy from the localized NBO of the idealized Lewis structure into an empty non-Lewis orbital. For each donor (i) and acceptor (j), the stabilization energy E2 associated with the delocalization i ? j is estimated as: ð2Þ

Eð2Þ ¼ DEij ¼ qi Fði; jÞ=ðei  ej Þ

Fig. 4. Experimental and theoretical Raman spectra of 3-thiophenecarboxylic acid.

intermolecular bonding and interaction among bonds and also provides a convenient basis for investigating charge transfer or conjugative interaction in molecular systems. The different topological parameters were analyzed using the Bader’s atoms in molecules (AIM) theory using the AIM2000 package [26]. Moreover, the changes in the thermodynamic functions were investigated for the different temperatures from the vibrational frequency calculations of title molecule.

ð2Þ

Here qi is the orbital occupancy, ei and ej are the diagonal elements and F(i,j) is the off-diagonal NBO Fock matrix element. The larger E(2) value, the more intensive is the interaction between electron donors and electrons acceptors, i.e. more donating tendency from electron donors to electron acceptors and greater the extent of conjugation of the whole system. Natural bond orbital analysis provides an efficient method for studying intra- and

Fig. 5. Correlation graphic between the calculated and experimental wavenumbers.

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

5

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

Table 1 Comparison of calculated geometrical parameters (bond lengths (Å) and bond angles (°)) of 3-thiophenecarboxylic acid monomer and dimer calculated by HF and DFT/B3LYP methods using 6-311++G(d,p) basis set with the corresponding theoretical and experimental values reported. Parameters Bond length

Monomer HF

a

DFT

C1@C2 C1AS5 C1AH6 C2AC3 C2AH7 C3@C4 C3AC9 C4AS5 C4AH8 C9AO10 C9@O12 O10AH11

1.343 1.729 1.071 1.437 1.072 1.351 1.477 1.712 1.070 1.329 1.185 0.946

1.361 1.739 1.079 1.432 1.080 1.374 1.473 1.720 1.078 1.359 1.209 0.968

RMSD

0.0609

0.0559

Bond angle C2AC1AS5 C2AC1AH6 S5AC1AH6 C1AC2AC3 C1AC2AH7 C3AC2AH7 C2AC3AC4 C2AC3AC9 C4AC3AC9 C3AC4AS5 C3AC4AH8 S5AC4AH8 C1AS5AC4 C3AC9AO10 C3AC9AO12 O10AC9AO12 RMSD

111.82 127.92 120.26 112.18 124.73 123.09 112.74 122.40 124.86 111.69 127.19 121.11 91.56 113.23 124.27

111.59 128.57 119.84 112.47 124.58 122.95 112.70 122.36 124.94 111.51 127.67 120.81 91.72 112.78 124.94

b

DFT (aug-cc-PVTZ) 1.37 1.71 1.08

1.73 1.08 1.36

0.0765 111.54 126.90 121.56

112.48

122.23 2.038

2.121

2.31

Intermolecular H-bond lengths (Å) and angles (°) C9AO12AH23 C9AO10AH11 O10  O24 O12H23  O22 a b,c,d

Expc,d

Dimer a

HF

a

DFT

a

1.343 1.730 1.071 1.437 1.072 1.351 1.476 1.711 1.070 1.306 1.199 0.960

1.361 1.739 1.079 1.432 1.080 1.374 1.473 1.719 1.078 1.323 1.230 0.999

0.0649

0.0487

111.80 127.94 120.25 112.17 124.67 123.15 112.74 122.88 124.37 111.69 127.08 121.22 91.58 114.15 122.41 123.44

111.58 128.58 119.83 112.46 124.53 123.00 112.70 123.01 124.29 111.54 127.49 120.97 91.71 114.37 121.94 123.68

1.830

1.439

110.68 131.02 2.784 1.823

110.33 126.67 2.664 1.664

1.508c/1.44d 1.699c/1.70d 1.00c 1.437c/1.41d 1.00c 1.406c/1.38d 1.474c/1.51d 1.708c/1.73d 1.00c 1.332c/1.32d 1.235c/1.24d 1.05c

106.31c/108.8d

113.26c/112.3d

112.45c/114.6d 122.8c/122.1d 124.75c/123.3d 110.35c/109.1d

97.98c/95.2d 115.05c/115.0d 121.36c/120.3d 123.55c/124.6d

109.6c 126.66c 2.662c

This works. Values are taken from Refs. [12,9,11].

Results and discussion Molecular geometry (monomer and dimer) The optimized structural parameters (bond lengths and angles) of the monomer and dimer molecular of the titled compound have been obtained by using the HF and B3LYP methods with 6311++G(d,p) basis set. The obtained results are compared with the theoretical resultants found by Chandra et al. [12] and also by X-ray crystal data [9,11]. All these results are reported in Table 1. The geometry-optimized structure of 3-TCA shows very close resemblance of the actual crystal structure of this molecule. The optimized structure of the molecule is mainly planar in agreement with the experimental results [9]. Taking into account that the molecular geometry in the gas phase may be differ from the solid phase, owing to the extended hydrogen bonding and staking interactions there is reasonable agreement between the calculated and experimental geometric parameters. From theoretical values, we can find that most of the optimized bond lengths and bond angles are slightly longer and shorter than experimental values, due to the theoretical calculations belong to isolated molecule in gaseous phase and the experimental results belong to molecule in solid state. Comparing bond angles and bond lengths of 3-TCA found by the two methods, we find that the DFT theory leads to geometrical parameters, which are much closer to experimental values.

The correlation equations between the calculated geometrical parameters (bond lengths and bond angles) and experimental XRD data are fitted by correlation coefficients and the corresponding fitting factors (R2) for these parameters are 0.98138, 0.98774, 0.96733 and 0.97741 respectively for the HF and DFT methods. The corresponding correlation graphics are shown in Fig. S1. Table 1 shows also a comparison of the calculated geometrical parameters, in terms of the root-mean-square deviation (rmsd) values, for the monomer and the dimer of 3-TCA using HF, DFT methods and those reported by Chandra et al. [12] with the corresponding parameters refined from X-ray data [9,11]. The results show that the DFT method using the 6-311++G(d,p) basis set reproduce the bond lengths and the bond angles better than the HF method and than for those found by Chandra et al., while low rmsd values are observed for the bond lengths (0.0487 Å) and for the bond angles (1.439°) of calculated with the DFT method when they are compared with those predicted by the HF method (0.0609 Å and 1.830°). The comparison of the rmsd values clearly shows, also, the utility of the use of the DFT method. In the present study the intermolecular hydrogen bond distances are calculated for the vacuum phase in the same basis sets which is 6-311++G(d,p) and are shown in the end of Table 1. The low discrepancies between the theory and experiment arise from the differences of the structure between the gas and solid phase. Therefore in order to investigate the influence of the presence of

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

6

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

the intermolecular interaction in the gas phase, the geometry optimization was also carried out for the dimer interaction in the titled molecule. The strong intermolecular interaction between O12AH23  O22 is observed equal to 1.664 Å and the distance between O12  O22 is about 2.664 Å. While the observed value gives excellent correlation with the calculated values which is found at 2.662 Å [9] since the difference between the calculated value and the experimental one is around 0.002 Å. The angle calculated between the C9AO10AH11 is 126.67° which correlate with experimentally observed value of 126.66° [9]. The predicted distance and angles calculated using DFT method are well within the range <3.0 Å for hydrogen bond interaction. The global minimum energy of 3-TCA monomer and dimer calculated by DFT method are 1947362.704 kJ mol1 and 3894793.833 kJ mol1, respectively. This interaction takes place through the two equivalent stable hydrogen-bonded OAH  O contacts, which result in improved stabilization. The interaction energy on dimer formation through the doubly hydrogen bonded interface was calculated using the super molecule method [27,28]. The hydrogen-bonded interaction energy of the formation of 3-TCA dimer (DE = Edimer  2  Emonomer) is 16.31 kcal mol1. The high values of the dipole moment of the 3-TCA molecule (1.7765 Debye) favorite the formation of the intermolecular hydrogen bond dimer. Besides, the zero value of dipole moment confirms the centrosymmetric of the dimer molecule. Charge distribution The calculation of atomic charges plays an important role in the application of quantum mechanical calculations to molecular systems [29] because the atomic charges affect dipole moment, molecular polarizability, electronic structure and a lot of properties of molecular systems [30]. The charge distributions over the atoms suggest the formation of donor and acceptor pairs involving the charge transfer in the molecule. Mulliken charges are calculated by determining the electron population of each atom as defined in the basic functions. The charge distributions calculated by the Mulliken [31] and NBO methods for the equilibrium geometry of 3-TCA molecule (monomer and dimer) were calculated using B3LYP level with 6-311++G(d,p) basis sets and were listed in Table S1. The results can, yet, better be represented in graphical form as shown in Fig. 6. The charge distribution of title molecule show all the hydrogen atoms are positively charged, whereas the magnitudes of the atomic charges on carbon atoms for the compound were calculated to be both positive and negative ranging from 0.578 to 1.212. When we compare the atomic charge for the all atoms, we note that the maximum atomic charge is obtained for C4. This is due to the attachment of negatively charged carbon C3 atom. The oxygen atoms are found to be negative charge as expected. Additional, it is worthy to mention that the sulfur exhibit negative charge also. The presence of large negative charge on oxygen atom and net positive charge on hydrogen atom may suggest the formation of intermolecular interaction and consequently promotes the formation of the hydrogen bond. Topological parameters Many theoretical researches show that, one of the most useful tools to characterize atomic and molecular interactions, principally hydrogen bonding, is the topological analysis using the Bader theory of ‘Atoms in molecules’ (AIM) [32–34]. According to AIM theory, any chemical bond including hydrogen bonding is characterized by the existence of bond critical points (BCP). This theory, on the basis of the value of electron density at the bond critical point and the electron density paths, delivers criteria for the existence of the hydrogen bond. According to results found in

Fig. 6. Atomic charge distribution of 3-thiophenecarboxylic acid monomer and dimer.

Refs. [35–38], a hydrogen bond exists if the electron density at the bond critical point is more than 0.002 au and the Laplacian of electron density is higher than 0.004 au. The Laplacian of electron density, which is the which is defined as the sum of the three eigenvalues of the Hessian, k1, k2 and k3, provides valuable information about the charge concentration (r2 q(rb) < 0, a close-shell type bonding) or charge depletion (r2 q(rb) > 0, a covalent type bonding) of electron distribution. For hydrogen bonds, qb is usually small and r2 q(rb) > 0, both being characteristic magnitudes of closed-shell interactions. Ellipticity (e), also provides a measure of the magnitude to which charge is favorably accumulated in given plane. The properties at BCPs are analyzed in terms of the following parameters: the electron density, its Laplacian, and the electron energy density (Hb). The components of Hb are also considered: the kinetic electron energy density (Gb) and the potential electron energy density (Vb). A balance between Gb and Vb, the total energy density Hb (=Gb + Vb), will give information about depletion or concentration of electron density, and hence the type of bonding. Molecular graphs of the monomer and the dimer using AIM2000 program [26] are shown in Fig. 7. In this, we have illustrated the different bond and ring critical points of 3-TCA monomer and dimer obtained by B3LYP/6-311++G(d,p) method. The topological analysis of the dimer shows two BCPs (two OAH  O hydrogen bonds) and three RCPs. Topological parameters for the studied dimer are given in Table 2. The qb values obtained in the present study and positive magnitude of r2 q(rb) reported in Table 2 are on the high side of the requirements to define a hydrogen bond and thus a strong interaction may be concluded. The energy of OAH  O hydrogen bonds can be calculated using the relationship deduced by Espinosa et al. [39] EHB = V(rb)/2. In case of 3-TCA dimer, EHB has been calculated to be 14.2445 kcal/mol by B3LYP method. The characteristics of the inter-molecular hydrogen bonding can also be predicted by the energetic properties of BCP associated with the interaction. The calculated value of the EHB affirmed that the hydrogen bond found in 3-TCA belong the strong hydrogen bonding [40,41]. The ratio Gb/qb can be also used to define the character of the interaction. This ratio may be larger than 1.0 for closed shell (hydrogen bonding, van der Waals interaction and ionic bonds) [32]. In the current study the ratio Gb/qb is 0.8368 which is close to 1.0 for the hydrogen bonding. Analogous results, in other compounds [42,43], with Gb/qb value slightly lower than 1.0 have been affirmed for extraordinarily strong hydrogen bonding. The critical point found in the intermolecular hydrogen bond is associated with two negative (k1 = 0.085

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

7

Fig. 7. AIM molecular graphic showing the different critical points (BCPs) (red small balls) and ring critical points (RCPs) (yellow small balls) of 3-thiophenecarboxylic acid monomer and dimer calculated with B3LYP/6-311++G(d,p) level. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Table 2 AIM analysis of the bond critical points (BCP) and ring critical points (RCP) for both cyclic dimer of 3-thiophenecarboxylic acid at B3LYP/6-311++G(d,p) level. Parameter

OAH

q(r) r2 q(r)

0.3189 2.2171

H  O 0.0478 0.1385

RCP1 0.0396 0.2447

RCP2 0.0396 0.2447

NRCP 0.0081 0.0318

k1 k2 k3 |k1/k3| H G V [(k1/k2)  1] G/q(rc)

1.6179 1.5965 0.9973 1.6223 0.6170 0.0626 0.6795 0.0134 0.1963

0.0850 0.0833 0.3069 0.2769 0.0054 0.0400 0.0454 0.0204 0.8368

0.0363 0.1299 0.1510 0.2404 0.0056 0.0556 0.0500 1.2794 1.404

0.0363 0.1299 0.1510 0.2404 0.0056 0.0056 0.0500 1.2794 1.404

0.0069 0.0114 0.0273 0.2527 0.0009 0.0070 0.0061 1.6053 0.8642

q(r) and r2 q(r) are given in e/a30 and e/a50; ki are given in a.u; RCP1: Unit 1; RCP2: Unit 2; NRCP: new RCP formed.

and k2 = 0.0833) and one positive Eigen values (k3 = 0.3069). The correlation between the negative and positive curvatures |k1|k3 is less than 1.0, as it generally occurs in a hydrogen bond interaction [32]. Upon dimerization, when we compared the dimer with the monomer, the charge density value decrease from 0.3593 to 0.3189. This decrease is due to the charge transfer from proton acceptor to the proton donor (OAH) bond. The above process increases the OAH bond length and weakens the bond and due to this, consequently the electrons are delocalized in the bond and so the charge density value decreases for the OAH bond of the dimer. Electrostatic potential, total electron density and molecular electrostatic potential The molecular electrostatic potential V(r), at a given point r(x, y, z) in the vicinity of a molecule, is defined in terms of the interaction energy between the electrical charge generated from the molecule electrons and nuclei and a positive test charge (a proton) located at r. The molecular electrostatic potential (MEP) is related to the electronic density (ED) and is a very useful descriptor for determining sites for electrophilic attack and nucleophilic reactions as well as hydrogen-bonding interactions [44–46]. To predict reactive sites for electrophilic and nucleophilic attack for the title molecule, electrostatic potential (ESP), ED and MEP at the B3LYP/

6-311++G(d,p) optimized geometry were calculated using the computer software Gauss view [20]. In the present study, the ESP, ED and the MEP map figures for 3-TCA molecule are shown in Fig. 8 and the MEP map figure for 3-TCA dimer is shown in Fig. S2. The ED plots for title molecule show a uniform distribution. However, it can be seen from the ESP figures, that while the negative ESP is localized more over the oxygen atoms and is reflected as a reddish blob, the positive ESP is localized on the rest of the molecules. This result is expected, because ESP correlates with electro negativity and partial charges. The MEP which is a plot of electrostatic potential mapped into the constant electron density surface is shown in the bottom of Fig. 8. The electrostatic potential increases in the order red < orange < yellow < green < blue. The negative (red and yellow) regions of MEP were related to electrophilic reactivity and the positive (blue) regions to nucleophilic reactivity. The importance of this later lies in the fact that it simultaneously displays molecular size, shape as well as positive, negative and neutral electrostatic potential regions in terms of colour grading and is very useful in research of molecular structure with its physiochemical property relationship [47–50]. The resulting surface simultaneously displays molecular size and shape and electrostatic potential value. From the MEP it is evident that the negative charge (red) covers the carbonyl oxygen atom (O12) with a minimum value of 0.07019 a.u, and the maximum positive region (blue) on carboxylic acid hydrogen atom (H11AO10) with a maximum value of 0.07019 a.u. This confirms the existence of an intermolecular OAH  O interaction.

UV–Vis spectra analysis Ultraviolet UV spectral study is very useful in determining the transmittance and absorption of an optically active material [51]. Non-linear optical material must have the transmittance spectra for practical purpose. The UV–Vis (i.e.) transition of electrons was calculated theoretically by time dependent (TD) DFT method with B3LYP level and 6-311++G(d,p) basis set. Recall that, Time-dependent density functional theory (TD-DFT) has recently emerged as a powerful tool for investigating the static and dynamic properties of the molecules in their excited states, allowing for the best compromise between accuracy and computational cost. The calculations are made in the gas and in many other solvent (ethanol, acetonitile

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

8

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

ED (Total electron density)

ESP (Electrostatic potential)

MEP (Molecular electrostatic potential)

Fig. 8. Total electron density (ED), electrostatic potential (ESP) and the molecular electrostatic potential (MEP) map in gas phase for 3TCA molecule.

and cyclohexane). Table 3 shows the experimentally observed allowed transitions reported by Chandra et al. [12] and our theoretically results. The major contributions of the transitions were designated with the aid of Swizard program [52]. The calculations of the molecular orbital geometry show that the visible absorption maxima of this molecule correspond to the electron transition between frontier orbital’s such as translation from HOMO to LUMO, HOMO1 to LUMO and from HOMO to LUMO+1. As can be seen from Table 3, the calculated absorption maximum values have been found to be 234.1, 200.2 nm in gas phase, 234.2, 200.3 nm in ethanol, 233.7, 200.0 nm in acetonitrile and 233.5, 200.4 nm in cyclohexane. In the case of gas phase, the strong transition at 234.1 and 200.2 nm is with an oscillator strength f = 0.2784 and 0.3256 with 5.30 and 6.19 eV energy gap. But, in the solvent solution the strong transition with the high oscillator strength is observed in for the case of the cyclohexane solution of 3-TCA monomer. In this later case, the calculated absorption maximum values have been found to be 233.5 and 200.4 nm with an oscillator strength f = 0.2916 and 0.3396 with 5.33 and 6.19 eV energy gap. The inspection of the Table 3 show that these predicts intense electronic transition are of p ? p⁄ type. The p ? p⁄ transitions were expected to occur fairly at lower wavelengths, due to the consequence of the extended aromaticity of the Thiophene ring, so the transition essentially corresponds to p ? p⁄ bands. Natural bond orbital analysis A valuable facet of the natural bond orbital (NBO) method is the information obtained about the interactions in both filled and

virtual orbital spaces that could supplement the analysis of both the intra- and inter-molecular interactions. That is way NBO analysis was proved to be an effective tool for chemical interpretation of hyper conjugative interaction and electron density transfer (EDT) from filled lone electron pairs of the n(Y) of the ‘‘Lewis base’’ Y into the unfilled anti-bond r⁄(XAH) of the ‘‘Lewis acid’’ XAH in XAH  Y hydrogen bonding systems [53]. The strength of the interaction between electron donors and electron acceptors, or the donating tendency from electron donors to electron acceptors and hence the extent of conjugation of the whole system is measured by the magnitude of energy of hyperconjugative interactions, E(2) value. Delocalization of electron density between occupied Lewis-type (bond or lone pair) NBO orbitals and formally unoccupied (anti-bond or Rydberg) non-Lewis NBO orbitals correspond to a stabilizing donor–acceptor interaction. In order to elucidate the intermolecular hydrogen bonding, intermolecular charge transfer (ICT), rehybridization, delocalization of electron density and cooperative effect due to LP(O) ? r⁄(OAH), NBO analysis was performed on the 3-TCA molecule at the DFT/B3LYP/6-311++G(dp) DFT level and the corresponding results are presented in Table 4. In this table summarized the stabilization energies of donor– acceptor interactions with more than 10 kJ mol1 determined by second order perturbation analysis of Fock matrix. The intermolecular OAH  O hydrogen bonds are formed by the orbital overlap between the n(O) and r⁄(OAH), which results in intermolecular charge transfer causing stabilization of the H-bonded systems. Therefore hydrogen-bonding interaction leads to an increase in ED of OAH anti-bonding orbital weakens the OAH bond. Thus the nature and strength of the intermolecular hydrogen bonding

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

9

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

Table 3 Calculated and observed absorption wavelength k, excitation energies (E), and oscillator strengths (f) and symmetry of 3-thiophenecarboxylic acid molecule using B3LYP/ 311++G(d,p) level. kExp (nm)

a

k (nm)b

E (eV)

255.0 240.1 234.1 202.9 201.3 200.2

4.86 5.16 5.30 6.11 6.16 6.19

254.9 240.4 234.2 203.0 201.4 200.3

b

f (a.u)

b

Symmetry

Major contribution (%)

0.0306 0.0001 0.2784 0.0010 0.0070 0.3256

A0 A00 A0 A00 A00 A0

H ? L(76) H2 ? L(92) H1 ? L(72) H ? L+2(64) H ? L+3(63) H ? L+1(59)

4.86 5.16 5.29 6.11 6.16 6.19

0.0312 0.0001 0.2832 0.0016 0.0064 0.3297

A0 A00 A0 A00 A00 A0

H ? L(76) H2 ? L(92) H1 ? L(72) H ? L+2(54), H ? L+3(33) H ? L+3(55), H ? L+2(41) H ? L+1(59), H1 ? L+1(23)

254.3 241.3 233.7 202.6 200.3 200.0

4.87 5.14 5.31 6.12 6.19 6.20

0.0302 0.0001 0.2763 0.0023 0.0047 0.3151

A0 A00 A0 A00 A00 A0

H ? L(84) H2 ? L(94) H1 ? L(80) H ? L+2(44), H ? L+3(43) H ? L+2(49), H ? L+3(47) H ? L+1(65), H1 ? L+1(26)

252.3 244.8 233.5 205.5 201.8 200.4

4.91 5.06 5.31 6.03 6.14 6.19

0.0333 0.0001 0.2916 0.0055 0.0020 0.3396

A0 A00 A0 A00 A00 A0

H ? L(73) H2 ? L(91) H1 ? L(70) H ? L+3(71) H ? L+2(76), H ? L+3(19) H ? L+1(58), H1 ? L+1(24)

Gas

Ethanol

239

203 Acetonitrile

236

200 Cyclohexane

241

205

Assignment: H = HOMO; L = LUMO; L+1 = LUMO+1; etc. a Taken from Ref. [12]. b This work.

can be explored by studying the changes in electron density in the vicinity of OAH hydrogen bonds. The NBO analysis, in comparison between monomer and dimer, clearly illustrate the existence of strong OAH  O intermolecular hydrogen bonding in 3-TCA. This investigation obviously clarifies the formation of tow intermolecular H-bonded interactions between n(O10), n(O22), and r⁄(O24AH11), r⁄(O12AH23) antibonding orbitals, respectively. The stabilization energy E(2) associated with hyperconjugative interactions LP2(O10) ? r⁄(O24AH11) and LP2(O22) ? r⁄(O12AH23) were respectively 21.25 kJ mol1 and 21.11 kJ mol1, which measure the extend of intermolecular hydrogen bonding. The difference in stabilization energy E(2) associated with the hyper conjugative interactions is considerable, which is due to the accumulation of ED (%EDO = 22.61 and %EDH = 77.39) in the OAH bond drawn not only from n(O) of the hydrogen acceptor but also from the entire molecule leading to its elongation and concomitant red shift of the OAH stretching wavenumber [54,55]. Furthermore, the total energy (DETotal) in the dimeric form (430.38 kJ mol1) is more the twice of the total energy in the monomeric form (191.44 kJ mol1). This analysis revels also, that the dimer form are more stable than the monomer form and justify the formation of the intermolecular hydrogen bonding. Molecular properties from orbital energies (Frontier molecular orbitals) The most important frontier molecular orbitals (FMOs) such as highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are very important parameters for quantum chemistry. They play a crucial part in the chemical stability of the molecule [56]. We can determine the way the molecule interacts with other species; hence, they are called the frontier

orbital. In this work Gauss-Sum 2.2 program [57] was used to calculate group contributions to the molecular orbitals (HOMO and LUMO) and prepare the density of the state (DOS) as shown in Fig. S3. DOS plot shows population analysis per orbital and demonstrates a simple view of the character of the molecular orbitals in a certain energy range. The HOMO is the orbital that primarily acts as an electron donor and the LUMO is the orbital that largely acts as the electron acceptor [58]. The gap between HOMO and LUMO characterizes the molecular chemical stability [59]. The frontier orbital gap helps identify the chemical reactivity and kinetic stability of the molecule. In the present study and in the subject to well evaluate the energetic behavior of the title compound, we carried out calculations in Gas and in many other solvent (ethanol, acetonitrile and cyclohexane). The energies of the important molecular orbitals: the second highest (lowest) and highest (lowest) occupied (unoccupied) MO’s and the value of energy separation between the HOMO and LUMO were calculated using B3LYP/6-311++G(d,p) and are presented in Table 5. The HOMO (HOMO1) and LUMO (LUMO+1) energies are predicted at TD-B3LYP method with 6311++G(d,p) basis set. Accordingly to the results, the 3-TCA molecule contains 33 occupied molecular orbitals and 179 unoccupied virtual molecular orbitals. Fig. 9 shows the distributions and energy levels of HOMO (HOMO1) and LUMO (LUMO+1) orbitals for the title molecule in gaseous phase. The positive phase is red and the negative one is green. It is clear from Fig. 8 that the isodensity plots for the HOMO is well localized with the ring. Generally, the atom occupied by more densities of HOMO should have stronger ability to detach an electron whereas; the atom with more occupation of LUMO should have ability to gain an electron [60]. It is clear from the figure that, the HOMO lying at 7.018 eV is a delocalized p orbital and it is located mainly over the all the C

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

10

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

Table 4 Second order perturbation theory analysis of Fock matrix on NBO basis for 3-thiophenecarboxylic acid monomer and dimer using B3LYP/6-311++G(d,p). Donor (i)

Acceptor (j)

E(2)a

E(i)  E(j)b

F(i,j)c

Monomer p(C1AC2) p(C3AC4) p(C3AC4) LP(2)S5 LP(2)S5 LP(2)O10 LP(2)O12 LP(2)O12 DET LP!r ¼ 54:22

p⁄(C3AC4) p⁄(C1AC2) p⁄(C9AO12) p⁄(C1AC2) p⁄(C3AC4) p⁄(C9AO12) r⁄(C3AC9) r⁄(C9AO10)

14.21 15.49 17.37 19.99 24.36 45.80 19.27 34.95

0.30 0.31 0.31 0.27 0.27 0.36 0.70 0.65

0.062 0.063 0.067 0.068 0.074 0.117 0.106 0.136

14.25 15.23 18.69 19.69 24.31 19.16 26.99 56.05 14.25 15.23 18.70 19.69 24.31 56.03 18.93 26.51 21.25 21.11

0.30 0.31 0.29 0.27 0.27 0.70 0.71 0.34 0.30 0.31 0.29 0.27 0.27 0.34 0.72 0.71 0.70 0.70

0.062 0.063 0.068 0.068 0.074 0.105 0.125 0.126 0.062 0.063 0.068 0.068 0.074 0.126 0.106 0.124 0.111 0.111

Dimer p(C1AC2) p(C3AC4) p(C3AC4) LP(2)S5 LP(2)S5 LP(2)O10 LP(2)O10 LP(2)O12 p(C13AC14) p(C15AC16) p(C15AC16) LP(2)S17 LP(2)S17 LP(2)O24 LP(2)O22 LP(2)O22 LP(2)O10 LP(2)O22 DET LP!r ¼ 133:95 a b c

DET LP!p ¼ 90:15 DET p!p ¼ 47:07 DETotal ¼ 191:44

p⁄(C3AC4) p⁄(C1AC2) p⁄(C9AO10) p⁄(C1AC2) p⁄(C3AC4) r⁄(C3AC9) r⁄(C9AO12) p⁄(C9AO10) p⁄(C15AC16) p⁄(C13AC14) p⁄(C21AO22) p⁄(C13AC14) p⁄(C15AC16) p⁄(C21AO22) r⁄(C15AC21) r⁄(C21AO24) r⁄(O24AH11) r⁄(O12AH23) DET LP!p ¼ 200:08 DET p!p ¼ 96:35 DETotal ¼ 430:38

E(2) means energy of hyper conjugate interactions (stabilization energy in kcal mol1). Energy difference between donor and acceptor i and j NBO orbitals in a.u. F(i,j) is the Fock matrix element between i and j NBO orbitals in a.u.

atoms of Thiophene ring and C@C group, and the HOMO (orbital 33) ? LUMO (orbital 34) transition implies an electron density transfer to the whole Thiophene ring and oxygen atoms. While the LUMO orbitals are p⁄ in type is lying at 1.600 eV. As a result, a very small energy gap is observed between HOMO and LUMO molecular orbitals and the energy gap calculated is 5.418 eV. Hence the probability of p ? p⁄ proton transition is highly possible between HOMO and LUMO orbitals for the 3-TCA. The lower value for frontier orbital gaps in case of 3-TCA makes it more reactive and less stable. A molecule with a small frontier orbital gap is more polarizable and is generally associated with high chemical reactivity, low kinetic stability and is also termed as soft molecule [61– 63]. The HOMO ? LUMO+1 transition imply an electron density transfer to the carboxylic group COOH of the 3-TCA molecule. In addition to the energy gap, the chemical hardness and softness of a molecule is a good indicator of the chemical stability of a molecule and the dipole moment in a molecule is another

important electronic property. For example, the bigger the dipole moment, the stronger will be the intermolecular interactions. All the calculated values of these quantum chemical parameters previously cited and other parameters (the electro negativity and the electrophilicity index) of the title molecule are presented in Table 5. Based on predicted dipole moment values, it is found that, in going from the gas phase (2.460 D) to the solvent phase (2.037 D in Cyclohexane) the dipole moment value increases. Thermodynamic properties One of important parameters of thermodynamics is the partition function. The partition function links thermodynamics, spectroscopy and quantum theory. The different types of partition functions are (i) translational partition function, (ii) rotational partition function, (iii) vibrational partition function and (iv) electronic partition function. Partition functions can be used to

Table 5 Calculated energy values, chemical hardness, electronegativity and dipole moment of 3-thiophenecarboxylic acid in gas, ethanol, aectonitrile and cyclohexane. TD-DFT/B3LYP/6-311++G(d,p)

Gas

Ethanol

Acetonitrile

Cyclohexane

Etotal (Hartree) EHOMO (eV) ELUMO (eV) DEHOMO–LUMO gap (eV) EHOMO1 (eV) ELUMO+1 (eV) DEHOMO1–LUMO+1 gap (eV) Electronegativity v (eV) Chemical hardness g (eV) Softness f (eV)1 Electrophilicity index (w) Dipole moment (Debye)

741.730 7.018 1.600 5.418 7.412 0.341 7.071 4.309 2.709 0.185 3.427 2.460

741.729 7.025 1.603 5.421 7.416 0.345 7.072 4.314 2.711 0.184 3.432 2.430

741.719 7.134 1.704 5.429 7.510 0.449 7.060 4.419 2.715 0.184 3.597 2.462

741.718 7.096 1.626 5.469 7.459 0.388 7.071 4.361 2.734 0.183 3.478 2.037

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

11

LUMO+1

-0.341eV

LUMO

-1.600eV

ΔE=-5.418eV

ΔE=-7.071eV Fig. 10. Variation of entropy (S), heat capacity (Cp), enthalpy (H) and Gibb’s free energy (G) with temperature for 3-thiophenecarboxylic acid molecule.

HOMO

-7.018eV

HOMO-1

-7.412eV

Fig. 9. The frontier and second frontier molecular orbitals of 3-hiophenecarboxylic acid.

calculate heat capacities, entropies, equilibrium constants and rate constants. The total energy of a molecule is the sum of translational, rotational, vibrational and electronic energies. i.e., E = Et + Er + Ev + Ee. The statistical thermo chemical analysis of 3-TCA is carried out considering the molecule to be at room temperature of 298.15 K and one atmospheric pressure. The thermodynamic parameters such as zero-point vibrational energy, thermal energy, specific heat capacity, rotational constants, entropy, and dipole moment of 3-TCA are calculated using B3LYP/6-311++G(d,p) basis set and listed in Table 6. The global minimum energy obtained for the optimized stable structure is 741.71112421 a.u. for the monomer and 1483.44830949 a.u. for the dimer. The variations in the zero point vibrational energy seem to be insignificant. On the basis of vibrational analysis the standard statistical thermodynamic functions such as heat capacity (Cp), entropy (S), Gibb’s free energy (G) and enthalpy changes (H) for various ranges (100–1000 K) of temperatures are determined and these results Table 6 The calculated thermodynamic parameters (at 298.15 K) of 3-thiophenecarboxylic acid monomer and dimer with DFT/B3LYP method using 6-311++G(d,p) basis set.

SCF energy E (a.u.) Zero-point vibrational energy (kcal mol1) Rotational constants (GHz) A B C Thermal energy (kcal mol1) Specific heat at constant volume Cv (cal mol1 K1) Entropy S (cal mol1 K1) Dipole moment (Debye)

Monomer

Dimer

741.71112421 51.10785

1483.44830949 103.27709

4.45277 1.16799 0.92529 55.407 25.391

2.22287 0.11535 0.10966 112.665 54.244

83.572 1.7765

128.464 0.0000

are presented in Table S2. The correlation equations between these thermodynamic properties and temperatures were fitted by parabolic formula. All the thermodynamic data provide helpful information for the further study on the title compound. From Table S2, it can be observed that these thermodynamic functions are increasing with temperature ranging from 100 to 1000 K due to the fact that the molecular vibrational intensities increase with temperature [64]. The corresponding fitting factors (R2) for these thermodynamic properties are 0.9987, 0.99993, 0.99918 and 0.99996, respectively. The corresponding fitting equations are as follows and the variations of these thermodynamic functions with temperature are graphically represented in Fig. 10.

C p ¼ 13:66141 þ 0:39478T  1:83973  104 T 2 ðR2 ¼ 0:9987Þ ð3Þ S ¼ 222:33708 þ 0:4635T  1:26458  104 T 2 ðR2 ¼ 0:99993Þ ð4Þ H ¼ 4:86832 þ 0:06071T þ 9:62102  105 T 2 ðR2 ¼ 0:99918Þ ð5Þ G ¼ 5:90484  0:2552T  1:61659  104 T 2 ðR2 ¼ 0:99996Þ

ð6Þ

All the thermodynamic data afford helpful information for the study of thermodynamic energies and estimate directions of chemical reactions according to the second law of thermodynamics in thermo chemical field [65]. It is to be mentioned that all thermodynamic calculations were done in gas phase and they could not be used in solution. Nonlinear optical properties and dipole moment Density functional theory has been used as an effective method to investigate the organic non-linear optical (NLO) materials. Recent research works have illustrated that the organic non-linear optical materials are having high optical non-linearity than inorganic materials [66]. In the presence of an applied electric field, the energy of a system is a function of the electric field. Polarizabilities and hyperpolarizabilities characterize the response of a system in an applied electric field [67]. They determine not only the strength of molecular interactions but also the cross sections of different scattering and collision processes, as well as the NLO properties of the system [68,69]. For this subject, in this study

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

12

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

the electronic dipole moment, molecular polarizability, anisotropy of polarizability and molecular first hyperpolarizability of present compound were investigated. The polarizability a and the hyper polarizability b and the electric dipole moment l of title compound are calculated by finite field method using B3LYP/6-311++G(d,p) basis set available in Gaussian 03 package. The polarizability and hyperpolarizability tensors (axx, axy, ayy, axz, ayz, azz and bxxx, bxxy, bxyy, byyy, bxxz, bxyz, byyz, bxzz, byzz, bzzz) can be obtained by a frequency job output file of Gaussian. However, a and b values of Gaussian output are in atomic units (a.u.) so they have been converted into electronic units (esu) (a; 1 a.u. = 0.1482  1024 esu, b; 1 a.u. = 8.6393  1033 esu). The complete equations for calculating the magnitude of total static dipole moment l, the mean polarizability total atot, the anisotropy of the polarizability Da and the mean first hyperpolarizability b0 can be calculated using the equations, respectively. 1

l ¼ ðl2x þ l2y þ l2z Þ2

The scaled calculated harmonic vibrational frequencies B3LYP/6311++G(d,p) basis set, observed vibrational frequencies, and detailed PED assignments are given in Table 7 and 8 respectively for the monomer and the dimer. All the calculated modes are numbered from the largest to the smallest frequency within each fundamental wave number. For visual comparison, the observed and simulated FT-IR and FT-Raman spectra are presented in Figs. 3 and 4. Note that the correlation between experimental and the theoretical spectra are good. The calculated spectra found to be close the experimental values with reasonable accuracy. Hydrogen atoms involved in intermolecular hydrogen bonds shows deviation in the simulated spectra with experimental spectra. This deviation is attributed to the fact that the theoretical spectrum was obtained in gas phase without considering the intermolecular hydrogen bonding effects. The vibrational analysis of 3-TCA was performed on the basis of the characteristic vibrations of the most important excited in the title molecule.

ð7Þ Carbon–Hydrogen vibrations

atotal

1 ¼ ðaxx þ ayy þ azz Þ 3

ð8Þ

i12 1 h Da ¼ pffiffiffi ðaxx  ayy Þ2 þ ðayy  azz Þ2 þ ðazz  axx Þ2 þ 6a2xz þ 6a2xy þ 6a2yz 2 ð9Þ h i1 2 2 2 2 b0 ¼ ðbxxx þ bxyy þ bxzz Þ þ ðbyyy þ byzz þ byxx Þ þ ðbzzz þ bzxx þ bzyy Þ ð10Þ

The dipole moment, polarizability and first hyperpolarizability are tabulated in Table S3. According to the present calculations, the dipole moment and mean polarizability of 3-TCA are found to be 1.7765 Debye and 11.993993  1024 esu, respectively. The lowest value of dipole moment is observed for component lx. In this direction, this value is equal to 1.3548 Debye. The magnitude of the molecular hyperpolarizability b, is one of key factors in NLO system. The calculated first static hyperpolarisability b0 value is equal to 1616.290  1033 esu. Urea is the prototypical molecule used in the study of the NLO properties of the molecular systems. Therefore urea was used frequently as a threshold value for comparative purposes. In this study, the total dipole moment of title molecule is greater than urea but the polarizability and the calculated b value are approximately the twice than those of urea. The l, a and b of urea are 1.525686 Debye, 5.0477  1024 esu and 780.324  1033 esu, respectively, obtained by B3LYP/6311++G(d,p) method. These results indicate that the title compound is a good candidate of NLO material. Vibrational spectral analysis The 3-TCA monomer consists of 12 atoms, which gives rise to 30 normal modes of vibrations. The monomer structure belongs to Cs point group symmetry, all the 30 normal vibration modes classified as 21 A0 (planar) + 9 A00 (out-of-plane) vibrations are active in both IR and Raman spectra. But, their dimeric form belongs to C2h point group symmetry and has 66 normal vibration modes classified as 23 Ag (planar) + 22 Bu (planar) + 11 Au (out-of-plane) + 10 Bg (outof-plane). The Au and Bu, vibrations are IR active while the Ag and Bg ones are Raman active. It is important to notice that the vibration modes predicted for the dimeric form with Au and Bu symmetries (IR active) or with Ag and Bg (Raman active) are observed in both spectra due to vibration modes corresponding to the monomer with CS symmetry and, also to that the acidic H atoms, involved in the formation of the centrosymmetric carboxylic dimer are disordered, as observed experimentally by Visser et al. [10].

In the present study, the three adjacent hydrogen atoms left around the thiophene ring of 3-TCA monomer give rise to three CAH stretching modes (v2, v3, v4), three CAH in-plane bending (v10, v11, v12) and three CAH out-of-plane bending (v15, v17, v20) modes. The aromatic and the heteroaromatic organic molecule show the presence of the CAH stretching vibrations in the 3250– 2950 cm1 range which is the characteristic region for the identification of CAH stretching vibrations [70] and principally the regions 3250–3100 cm1 for asymmetric stretching and 3100–2950 cm1 for symmetric stretching modes of vibration [71]. Many authors [71–75] show that, the nature of substituents cannot affect much to the bands in this region. The CH in-plane bending vibrations appear by sharp but weak to medium bands in the 1300– 1000 cm1 region [71,73]. These bands are not sensitive to the nature of substituents [72]. The out-of-plane bending vibrations occur in the wavenumber range 1000–675 cm1 [70,76]. Accordingly, the CAH stretching modes of 3-TCA monomer are observed in FT-IR at 3108, 3098 and 3047 cm1 and at 3111 cm1 in FT-Raman. In dimer, these stretching modes are assigned to 3113, 3105 and 3082 cm1 in FT-IR. They are very pure modes since their TED contributions are almost greater than 98%. The observed bands at 1202, 1111 and 1031 cm1 in the FT-IR spectrum and the bands at 1204 and 114 cm1 in the FT-Raman spectrum are due to CAH in plane bending modes. The calculated values of this modes show better agreement with the experimental values. While in the dimer these modes are associated with the bands between 1163 and 1041 cm1. The CAH out-of-plane bending deformations CAH inplane bending modes of 3-TCA monomer are assigned to 876, 827 and 703 cm1 in FT-IR. The scaled theoretical values of CAH out-of plane bending modes calculated at B3LYP/6-311++G(d,p) show good agreement with the experimental values. These results agree with the literature data [77,78]. The TED contribution to these modes indicates that, CAH out-of-plane bending modes are also highly pure modes like CAH stretching modes. For the dimer structure, the calculated CAH out-of-plane bending are associated with the bands between 871 and 667 cm1. These results are supported by the findings given in the literature [70,76]. Thiophene ring vibrations The C@C vibrations are one of the most important vibrations of the aromatic ring. Due to this important stretching vibration in the spectrum, the Thiophene derivatives have a highly characteristic of the aromatic ring. In the literature [79], the Thiophene derivatives have medium to strong bands in the ranges 1610–1560, 1520– 1470 and 1400–1390 which are due principally to the C@C ring

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

13

Table 7 Calculated vibrational frequencies and mode assignments calculated frequencies at B3LYP/6-311++G(d,p) level for 3-thiophenecarboxylic acid monomer. No

Si

1 2 3 4

A0 A0 A0 A0

Observed frequencies Infrared

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A00 A0 A00 A0 A00 A00 A0 A0 A00 A00 A0 A00 A0 A0 A00 A00

Raman

3108ms 3098mw 3047m 2968m 2889m 2754ms 2707ms 2634m 2551ms 1692s 1444w 1378s

3111m

1286w 1202m 1111s 1031ms 1025ms 905m 876w 838ms 827m 748s

1280m 1204w 1114mw

703ms 626ms 572ms 540ms

1651ms 1386m

871w 826s 758w 712w 626m 572w 501w 459mw 425mw

121m 106mw

Ii

Calculated frequencies Unscaled

Scaled

3772 3258 3249 3223

3574 3085 3077 3053

1785 1560 1458 1430 1339 1242 1176 1104 1089 934 917 871 837 814 761 705 682 627 604 536 493 458 381 189 168 75

1686 1473 1376 1349 1263 1169 1108 1038 1025 878 862 818 786 764 713 660 638 586 564 500 459 426 352 170 150 62

100.56 5.20 0.29 1.87

460.80 31.29 43.41 43.49 53.62 77.73 155.18 126.89 50.02 8.35 0.57 28.75 10.92 6.77 107.854 22.26 37.94 15.95 22.94 68.11 7.53 2.97 5.02 2.10 0.87 0.87

Ra

18.60 20.08 27.20 15.36

100 28.27 68.65 12.66 1.87 16.18 34.82 3.13 8.51 23.62 0.81 11.91 1.51 56.66 0.14 0.06 16.52 33.75 2.56 14.42 9.00 1.13 38.51 1.14 17.59 0

Vibrational assignments(% PED)

mOH(100) mCH(98) mCH(99) mCH(100) Overtone + combination Overtone + combination Overtone + combination Overtone + combination Overtone + combination Overtone + combination mO@C(86) mC@C(71), bHCC(11) mC@C(73) mCC(66) bH11O10C9(66) bHCC(83) bHCS(77), mCC(12) mC@C(11), bHCC(54), mOC(18) bHOC(10), bHCC(21), mOC(47) mCC(26), bCCC(17), bOCO(23) dHCSC(97) mSC(78) dHCSC(89) mSC(69), bCSC(10) dHCSC(94) dHCCC(95) mOC(10), mSC(11), bCCC(62) bCSC(72) dH11O10C9O12(84) dH11O10C9C3(87) bCCO(76) dCCCS(75) mCC(23), mSC(10), bOCO(56) bCCC(88) dCCCS(92) cCCCO(96)

m, b and d denote stretching, in-plane bending and torsion modes, respectively. Ii: infrared intensity, Ra: Raman intensity, s: strong, m:medium, ms: medium strong, mw: medium weak, w: weak. PED: potential energy distribution data are taken from VEDA4.

stretching vibrations. For example, the C@C stretching was observed for the 3-ethynythiophene molecule [80] at 1516 cm1. In the present work, the vibrations were observed at 1444, 1378 and 1031 cm1 in the FT-IR spectrum and at 1386 cm1 in the FT-Raman spectrum. These modes have been calculated for the 3-TCA at 1473, 1376 and 1038 cm1, respectively. The PED contributions to these modes are 71%, 73% and 11% respectively. The CAC modes were observed at 1111 cm1 in the FT-IR and at 1114 cm1 in the FT-Raman spectrum. These modes have been calculated at 1349 and 1108 cm1 and assigned by PED. Carbon–sulfur vibrations Socrates has been shows that the CAS stretching vibrations are expected to appear in the 1035–245 cm1 frequency range and his band has a variable intensity in the IR spectra, whereas, in Raman spectra has a strong bands [79]. For this, the assignment of this later is difficult in the infrared in different compounds, but easy to identify in the Raman spectra. Besides, the CAS bands cannot be distinguished in Thiophene. This fact can be explained due to the shorter bond length and higher polarity of the CAS bond in Thiophene [81]. Karabacak et al. [82] predicted that the CAS stretching mode occurs at 691, 707 cm1 and is observed at 743 and 771 cm1. Klots et al. [83] assigned this mode at 872, 753 cm1and 870, 750 cm1 in both the vapor and liquid phases, respectively. In this work, the CAS stretching vibrations are assigned to a very strong intensity IR bands observed at 838 and 748 cm1, medium strong intensity IR bands observed at 626 cm1 and a strong

intensity Raman band at 826 cm1, respectively. These modes have been calculated at 818, 764 and 638 cm1, respectively. Carboxylic acid group vibrations Generally the vibrational analysis of the carboxylic acid group is more important because the dimeric characteristic of the molecule arises mainly due to the presence of this moiety or a group [84]. The carboxylic acid dimer is formed by strong hydrogen bonding in the solid and liquid state. Hence the derivatives of carboxylic acids are best characterized by the carbonyl and hydroxyl groups. The presence of hydroxyl group vibrations are probable to be the most sensitive to the environment, hence they show pronounced shifts in the spectra of the hydrogen bonded species. A non-hydrogen bonded absorbs strongly in the region 3700–3584 cm1, whereas the existence of intermolecular hydrogen bond formation can lower the OAH stretching frequency [85,86] in the range 3500–3200 cm1. Besides, the carbonyl group is important in the infrared spectrum since of its strong intensity of absorption and high sensitivity towards relatively minor changes in its environment also. The hydroxyl stretching vibrations are commonly observed in the region 3600–2900 cm1 [87], but the C@O stretching of carboxylic acids is expected in the region 1800–1680 cm1 [88,89]. In the present study, the strong band at 1692 cm1 in FT-IR and the band at 1657 cm1 in FT-Raman are assigned to C@O stretching. The IR bands at 3108, 3047 and 2968 cm1 is clearly assigned to OAH stretching modes of monomer and dimer, as observed in Tables 7 and 8. The red shift of OAH stretching

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

14

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

Table 8 Calculated vibrational frequencies and mode assignments calculated frequencies at B3LYP/6-311++G(d,p) level for 3-thiophenecarboxylic acid dimer. No

C2h

Calculated frequencies Unscaled

Scaled

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66

Bu Ag Ag Bu Ag Bu Bu Ag Bu Ag Bu Ag Ag Bu Ag Bu Ag Bu Bu Ag Bu Ag Ag Bu Ag Bu Au Ag Bu Au Bg Bg Ag Bu Au Bg Bu Ag Bg Au Bu Ag Bg Au Bu Ag Bg Au Bu Ag Bg Au Ag Bu Bu Ag Bg Au Ag Ag Au Bg Bg Bu Au Au

3257 3257 3249 3249 3224 3224 3197 3104 1726 1686 1559 1557 1486 1475 1452 1449 1419 1411 1313 1306 1222 1220 1135 1132 1095 1095 984 942 942 918 918 911 873 873 842 839 822 819 765 765 740 721 705 705 633 633 579 577 542 508 462 462 425 388 264 238 195 182 111 101 93 83 59 56 39 7

3113 3113 3105 3105 3082 3082 3056 2967 1646 1608 1486 1484 1416 1405 1383 1380 1352 1344 1250 1243 1163 1161 1079 1077 1041 1041 935 894 894 871 871 865 828 828 799 796 779 777 725 725 701 683 667 667 598 598 547 545 511 479 434 434 399 364 245 220 179 166 98 88 81 71 48 45 29

Ii

Ra

Major assignments(% PED)

14.08 0 0 1.33 0 0.16 5604.85 0 1209.86 0 124.20 0 0 361.89 0 10.48 0 53.07 783.15 0 37.80 0 0 54.46 0 15.93 211.00 0 16.82 0.56 0 0 0 71.79 41.80 0 22.39 0 0 116.75 61.59 0 0 36.02 15.68 0 0 9.59 80.86 0 0 0.01 0 3.69 79.37 0 0 0.05 0 0 0.66 0 0 2.73 0.03 0.83

0 9.68 16.28 0 7.31 0 0 68.65 0 100 0 16.58 9.90 0 40.36 0 32.89 0 0 38.43 0 1.66 6.81 0 4.23 0 0 13.96 0 0 0.43 0.50 4.01 0 0 1.54 0 35.96 0.211 0 0 1.55 0.01 0 0 19.77 0.64 0 0 3.06 1.56 0 35.19 0 0 5.99 7.64 0 1.46 0.93 0 0 0 0 0 0

mCH(98) mCH(98) mCH(98) mCH(98) mCH(99) mCH(99) mOH(99) mOH(94) mO@C(78) mCC(71), bOHO(18) mC@C(64), bHCC(17) mC@C(61), bHCC(18) mCC(10), mOC(20), bOHO(42) mCC(48), bHOC(20), mC@C(76) mC@C(71) mCC(31), bHCS(13), bOAH  O(19) mCC(20), bHOC(46), bHCS(15) bHOC(19), mOC(19), bHCC(14), bHCS(13) mOC(42), bHCS(12), bOAH  O(12) bHCC(68) mOC(13), bHCS(64) mCC(26), bHCS(51) mOC(33), bHCS(51) mC@C(13), bHCC(67) mC@C(13), bHCC(77) dC@O  HAO(84) mCC(38), bCCC(21) mCC(37), bOCO(20) dHCCC(79) dHCCC(88) dC@O  HAO(87), dCCCC(10) mSC(60), bCCC(15) mSC(58), bOCO(11) cCOOC(29), dHCCC(57) dHCCC(54), cCOOC(27) mSC(72) mSC(76) dHCCC(30), cCOOC(50), dHOCO(10) dCOOC(54), dHCCC(31) mSC(10), bOCO(65) bOCO(63) dHCSC(87) dHCSC(86) mSC(11), bCCS(72) bCCS(71), mSC(11) cCCCC(69) cCCCC(82) bCCO(76) bCCC(76) cCCCC(12), dCCCS(70) dCCCS(89) bCCC(32), mCC(35) mCC(27), mSC(11), bOCO(50) bCCC(76) bHOC(90) dCCCS(11), dCCCC(74) cCCCC(86) mOH(66), mCC(13) bHOC(86) dH  OCO(89) dCCCO(79) dCCCO(17), dHOCO(69) bCCO(91) dCOHO(96) dHOCO(87)

m, b, d and c denote stretching, in-plane bending, torsion, and out-of-plane bending modes, respectively. Ii: infrared intensity, Ra: Raman intensity, s: strong, m: medium, ms: medium strong, mw: medium weak, w: weak. PED: potential energy distribution data are taken from VEDA4.

wavenumber from 3108 cm1 in the monomer to 3047–2968 cm1 in the dimer confirms the intermolecular OAH  O hydrogen bonding in the molecule [90]. According to TED results, the OAH stretching is a pure mode contributing (94–100%). The wavenum-

bers of these modes calculated by DFT are in excellent agreement with the experimental FT-IR and FT-Raman wavenumbers. In addition, the absence of the observed OAH stretching in the FT-IR spectrum is due to the presence of the intermolecular hydrogen

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

bonding. According to calculated frequencies, one may conclude that upon dimerization the OAH stretching vibration is downshifted due to the presence of intermolecular interaction. The CAO stretching of the carboxylic acid group is highly coupled with the vibrations of adjacent group OAH in plane bending. The bands arising from CAO stretching and OAH in-plane bending vibrations appear in the regions 1320–1210 cm1 and 1440– 1400 cm1, respectively [91]. These vibrations are calculated at 1025 cm1 for the 3-TCA monomer and at bands 1416, 1405, 1250, 1243 cm1 for the dimer. For a hydrogen bonded molecule the OAH out-of-plane bending mode lies in the region of 751– 710 cm1 [92]. For our studied dimer, the calculated vibration modes at 935 and 905 cm1 are assigned to the OAH out-of-plane bending vibrations. The bands observed at 1025 cm1 in the FT-IR spectrum and at 871 cm1 in the Raman spectrum are most likely due to the OAH out-of-plane bending vibrations. The hydrogen bond stretching vibration is theoretically observed at 98 cm1. In the end of this assignment you must recall that, in the FT-IR spectrum, the bands in the region 2968–2551 cm1 may be due to the non-fundamental bands of the thiophene ring. These vibrational bands are broad, very sharp and less intense. That is why; these bands were assigned in terms of various fundamentals, overtone and combination vibrations. Conclusion In the first step of this research, calculations performed at two levels of theories: Hartree–Fock and density functional theory. The density functional theory confirms the following two facts: (i) the ability of DFT method to reproduce X-ray crystallographical structure of 3-thiophenecarboxylic acid with a reliable agreement and (ii) there is a close accuracy between the DFT computations for the prediction of geometry when we compared with the Hartree– Fock method. A complete vibrational analysis of 3-TCA have been performed DFT-B3LYP method with 6-311++G(d,p) basis sets. The influences of many functional groups to the vibrational frequencies of the title compound were discussed. The observed and calculated spectra are agree well when DFT frequencies are scaled. The less standard deviation between theoretical and experimental wavenumber is confirmed by the qualitative agreement between the calculated and observed frequencies. The vibrational spectral analysis reveals that the existence of strong OAH  O intermolecular interaction can be observed by the broadness, red shifting of wavenumber and strength of OH stretching mode and unusual lowering of carbonyl stretching wavenumber. Topological feature at bond critical point as obtained from the AIM theory and NBO analysis confirms also the presence of intermolecular OAH  O in 3-TCA. Furthermore, the thermodynamic and electronic absorption properties of the compounds have been calculated. Temperature dependence of some statistical quantities has been investigated. It was seen that the heat capacities, entropies and enthalpies increase with the increasing temperature owing to the intensities of the molecular vibrations increase with increasing temperature. The other molecular properties such as Mulliken atomic charges, polarizability and hyperpolarizability and HOMO–LUMO gaps have also been discussed. Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.saa.2014.10.008. References [1] A. Achson, An Introduction to the Chemistry of Heterocyclic Compounds, third ed., Wiley-Intersciences, India, 2009.

15

[2] N.B. Patel, F.M. Shaikh, Sci. Pharm. 78 (2010) 753–765. [3] S. Gronowitz (Ed.), Thiophene and Thiophene Derivatives, vols. 1–4, WileyInterscience, New York, 1985. [4] O. Meth-Cohn, Comp. Org. Chem. 4 (1979) 789–838. [5] R.M. Kellog, Comp. Heterocyclic Chem. 4 (1984) 713–740. [6] J.B. Press, R.K. Russell, Prog. Heterocyclic Chem. 2 (1990) 50. [7] G. Pistolis, C.M. Paleos, A. Malliaris, J. Phys. Chem. 99 (1995) 8896–8902. [8] A.J. Beveridge, G.C. Heywood, Biochemistry 32 (1993) 3325–3333. [9] P. Hudson, J.H. Robertson, Acta Cryst. 17 (1964) 1497–1505. [10] G.J. Visser, G.J. Heeres, J. Wolters, A. Vos, Acta Cryst. B24 (1968) 467–473. [11] D.R. Shridhar, C.V.R. Sastry, S.C. Chaturvedy, R. Grumurthy, P.P. Sing, C.S. Rao, A.Y. Junnarkar, Indian J. Chem. 23 (1984) 692–694. [12] S. Chandra, J. Chowdhury, M. Ghosh, G.B. Talapatra, J. Phys. Chem. C 115 (2011) 14309–14324. [13] Y. Zhang, R.H. Holm, J. Am. Chem. Soc. 125 (2003) 3910–3920. [14] N.J. Long, Angew. Chem. Int. Ed. Engl. 34 (1995) 21–38. [15] Gaussian Inc., Gaussian03 Program, Gaussian Inc.: Wallingford, 2004. [16] A.D. Becke, J. Chem. Phys. 98 (1993) 5648–5652. [17] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 85–789. [18] M.H. Jamroz, SPESCA Program, ICRI, Warsaw, 2002. [19] M.H. Jamróz, Vibrational Energy Distribution Analysis, VEDA 4, computer program, Poland, 2004. [20] R.I. Dennington, T. Keith, J. Millam, GaussView, Version 5.0.8, Semichem. Inc., Shawnee Mission, KS, 2008. [21] G. Keresztury, Raman spectroscopy theory, in: J.M. Chalmers, P.R. Griffith (Eds.), Handbook of Vibrational Spectroscopy, vol. 1, John Wiley & Sons Ltd., New York, 2002. [22] G. Keresztury, S. Holly, J. Varga, G. Besenyei, A.Y. Wang, J.R. Durig, Spectrochim. Acta 49 (1993) 2007–2026. [23] E.D. Glendening, J.K. Badenhoop, A.D. Reed, J.E. Carpenter, F. Weinhold, NBO 3.1; Theoretical Chemistry Institute, University of Wisconsin; Madison, WI, 1996. [24] M. Szafran, A. Komasa, E.B. Adamska, J. Mol. Struct. Theochem. 827 (2007) 101–107. [25] E.D. Glendening, C.R. Landis, F. Weinhold, WIREs Comput. Mol. Sci. (2011) 1– 42. [26] F. Biegler-Köning, J. Schönbohm, D. Bayles, AIM2000; a program to analyze and visualize atoms in molecules, J. Comput. Chem. 22 (2001) 545–559. [27] P. Hobza, R. Zahradnik, Intermolecular Complexes, Elsevier, Amsterdam, 1988. [28] F.B. van Duijneveldt, J.G.C.M. van Duijneveldt-van de Rijdt, J.H. van Lenthe, Chem. Rev. 94 (1994) 1873–1885. [29] S. Gunasekaran, S. Kumaresan, R. Arunbalaji, G. Anand, S. Srinivasan, J. Chem. Sci. 120 (2008) 315–324. [30] I. Sidir, Y.G. Sidir, M. Kumalar, E. Tasal, J. Mol. Struct. 964 (2010) 134–151. [31] R.S. Mulliken, J. Chem. Phys. 23 (1955) 1833–1840. [32] R.F.W. Bader, Atoms in Molecules: A Quantum Theory, Oxford Uni. Press, Oxford, 1990. [33] R.F.W. Bader, Chem. Rev. 91 (1991) 893–928. [34] B.F. Minaev, G.V. Baryshnikov, V.A. Minaeva, Dyes Pig. 92 (2011) 531–536. [35] I. Majerz, A. Koll, Acta Crystallogr. B60 (2004) 406–415. [36] P.L.A. Popelier, R.F.W. Bader, J. Phys. Chem. 98 (1994) 4473–4481. [37] U. Koch, P.L.A. Popelier, J. Phys. Chem. 99 (1995) 9747–9754. [38] E. Espinosa, I. Alkorta, I. Rozas, J. Elguero, R. Molins, Chem. Phys. Lett. 336 (2001) 457–461. [39] E. Espinosa, E. Molins, C. Lecomte, Chem. Phys. Lett. 285 (1998) 170–173. [40] G.A. Jeffrey, An Introduction to Hydrogen Bonding, Oxford University Press, New York, 1997. [41] G.R. Desiraju, T. Steiner, The Weak Hydrogen Bond in Structural Chemistry and Biology, Oxford University Press Inc, New York, 1999. [42] D.E. Hibbs, J. Overgaard, R.O. Plitz, Org. Biomol. Chem. 1 (2003) 1191–1198. [43] M.T. Caroll, C. Chang, R.F.W. Bader, Mol. Phys. 63 (1988) 387–405. [44] N. Okulik, A.H. Jubert, Internet Electron J. Mol. Des. 4 (2005) 17–30. [45] E. Scrocco, J. Tomasi, Adv. Quantum. Chem. 11 (1978) 115–121. [46] F.J. Luque, J.M. Lopez, M. Orozco, Theor. Chem. Acc. 103 (2000) 343–345. [47] J.S. Murray, K. Sen, Molecular Electrostatic Potentials, Concepts and 399 Applications, Elsevier, Amsterdam, 1996. [48] I. Alkorta, J.J. Perez, Int. J. Quant. Chem. 57 (1996) 123–135. [49] F.J. Luque, M. Orozco, P.K. Bhadane, S.R. Gadre, J. Phys. Chem. 97 (1993) 9380– 9384. [50] J. Sponer, P. Hobza, Int. J. Quant. Chem. 57 (1996) 959–970. [51] C.N.R. Rao, Ultraviolet and Visible Spectroscopy, Chemical Applications, Plenum Press, New York, 1975. [52] S.I. Gorelsky, SWizard Program Revision 4.5, University of Ottawa, Canada, 2010. . [53] F. Weinhold, C.R. Landis, Valency and Bonding: A Natural Bond Orbital Donor– Acceptor Perspective, Cambridge University Press, Cambridge, 2005. [54] V. Alabugin, M. Manoharan, S. Peabody, F. Weinhold, J. Am. Chem. Soc. 125 (2003) 5973–5987. [55] J. Chocholoussova, V. Spirko, P. Hobza, Phys. Chem. Chem. Phys. 6 (2004) 37– 41. [56] S. Gunasekaran, R.A. Balaji, S. Kumeresan, G. Anand, S. Srinivasan, Can. J. Anal. Sci. Spectrosc. 53 (2008) 149–162. [57] N.M. O’Boyle, A.L. Tenderholt, K.M. Langer, J. Comput. Chem. 29 (2008) 839– 845. [58] G. Gece, Corros. Sci. 50 (2008) 2981–2992. [59] D.F.V. Lewis, C. Ioannides, D.V. Parke, Xenobiotica 24 (1994) 401–408.

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008

16

N. Issaoui et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx

[60] P.S. Kumar, K. Vaudevan, A. Prakasam, M. Geetha, P.M. Anbarasan, Spectrochim. Acta A 77 (2010) 45–50. [61] A. Rauk, Orbital Interaction Theory of Organic Chemistry, second ed., WileyInterscience, New York, 2001. p. 86. [62] A. Streitwieser Jr., Molecular Orbital Theory for Organic Chemists, Wiley, New York, 1961. [63] K. Fukui, Science 218 (1982) 747–753. [64] J. Bevan Ott, J. Boerio-Goates, Calculations from Statistical Thermodynamics, Academic Press, 2000. [65] R. Zhang, B. Du, G. Sun, Y. Sun, Spectrochim. Acta A 75 (2010) 1115–1124. [66] N.B. Singh, O.P. Singh, N.P.S.N. Singh, Y.P. Singh, N.B. Singh, Prog. Crystal Growth Charact. 44 (169) (2002) 169–174. [67] C.R. Zhang, H.S. Chen, G.H. Wang, Chem. Res. Chin. U 20 (2004) 640–646. [68] Y. Sun, X. Chen, L. Sun, X. Guo, W. Lu, Chem. Phys. Lett. 381 (2003) 397–403. [69] O. Christiansen, J. Gauss, J.F. Stanton, Chem. Phys. Lett. 305 (1999) 147–155. [70] G. Socrates, Infrared Characteristic Group of Frequencies, John Wiley & Sons, New York, 1980. [71] G. Varsanyi, Assignments for Vibrational spectra of Seven Hundred Benzene Derivatives, vols. 1 and 2, Academic Kiaclo, Budapest, 1973. [72] J. Mohan, Organic Spectroscopy – Principles and Applications, second ed., Narosa Publishing House, New Delhi, 2001. [73] K. Akhbari, A. Morsali, J. Iran. Chem. Soc. 5 (2008) 48–56. [74] S. Gunasekaran, U. Ponnambalam, S. Muthu, S. Ponnusamy, Asian J. Chem. 16 (2004) 1513–1518. [75] J. Fulara, M.J. Nowak, L. Lapinski, A. Les´, L. Adamowicz, Spectrochim. Acta Part A 47 (1991) 595–613. [76] N.B. Colthup, L.H. Daly, S.E. Wiberley, Introduction to Infrared and Raman Spectroscopy, Academic Press Inc, London, 1964.

[77] I. Sidir, Y.G. Sidir, E. Tasal, C. Ögretir, J. Mol. Struct. 980 (2010) 230–244. [78] E. Tasal, M. Kumalar, Spectrochim. Acta Part A 96 (2012) 548–562. [79] G. Socrates, Infrared and Raman Characteristic Group Frequencies-Table and Charts, third ed., John Wiley & Sons Ltd, Chichester, 2001. [80] J. Svoboda, J. Sedlacek, J. Zednik, G. Dvorakova, O. Trhlikova, D. Redrova, H. Balcar, J. Vohlidal, J. Pol. Sci. 46 (2008) 2776–2787. [81] C.I. Sainz-Diaz, M. Francisco-Marquez, A. Ivier-Bunge, Theor. Chem. Acc. 125 (2010) 83–95. [82] M. Karabacak, M. Çınar, M. Kurt, J. Mol. Struct. 968 (2010) 108–114. [83] T.D. Klots, R.D. Chirico, W.V. Steele, Spectrochim. Acta A 5 (50) (1994) 765– 795. [84] N. Sundaraganesan, B. DominicJoshua, C. Meganathan, R. Meenashi, J.P. Cornad, Spectrochim. Acta A 70 (2008) 376–383. [85] V. Krishnakumar, R. John Xavier, Indian J. Pure Appl. Phys. 41 (2003) 95–98. [86] R.M. Silverstein, F.X. Webster, Spectrometric Identification of Organic Compounds, sixth ed., John Wiley Inc, New York, 2003. [87] B. Smith, Infrared Spectral Interpretation, CRC Press, Boca Raton, FL, 1996. [88] L.J. Bellamy, The Infrared Spectra of Complex of molecules, vol. 1–2, Chapmann and Hall, London, 1975. [89] Ö. Alver, C. Parlak, M. Senyel, Spectrochim. Acta A 67 (2007) 793–801. [90] M. Samsonowicz, T. Hrynaskiewicz, R. Swislocka, E. Regulska, W. Lewandowski, J. Mol. Struct. 744 (2005) 345–352. [91] D.N. Sathyanarayana, Vibrational Spectroscopy – Theory and Applications, second ed., New Age International Publishers, New Delhi, 2007. [92] S. Sebastian, N. Sundaraganesan, S. Manoharan, Spectrochim. Acta A 74 (2009) 312–323.

Please cite this article in press as: N. Issaoui et al., Molecular structure, vibrational spectra, AIM, HOMO–LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree–Fock and density functional theory, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), http://dx.doi.org/10.1016/j.saa.2014.10.008